The present invention relates to an automotive vehicle body structure for improving the crash safety of the vehicle.
It has been proposed to control the deceleration of the passenger compartment of a vehicle by appropriately selecting the deformation mode of the part of the vehicle body other than the passenger compartment at the time of a vehicle crash, and prevent the deformation of the vehicle body from reaching the passenger compartment as a part of efforts to increase the protection of the vehicle occupants at the time of a vehicle crash (see Japanese patent laid open publication No. 7-101354 and others).
In view of reducing the injury to the vehicle occupant at the time of a vehicle crash, it is important to note that there is a delay in the deceleration of the vehicle occupant with respect to the deceleration of the vehicle body because the passenger restraint system such as a seat belt acts like a spring at the time of a vehicle crash, and the peak of the vehicle occupant deceleration occurs at the time of the maximum elongation of the spring although the vehicle body deceleration remains constant. Furthermore, this peak is significantly greater than the average deceleration of the vehicle body because the vehicle occupant reduces its speed in a shorter period of time than the main part of the vehicle body. Therefore, to reduce the maximum level of the vehicle occupant deceleration, it is necessary not only to reduce the average deceleration of the vehicle body but also to reduce the overshoot of the vehicle occupant deceleration due to the action of the restraint system as a spring.
In view of reducing the injury to the vehicle occupant, the waveform of the vehicle body deceleration is highly important. FIG. 14 shows a waveform of the vehicle body deceleration G2 which can minimize the vehicle occupant deceleration G1 according to the foregoing considerations. The vehicle body deceleration G2 in this case means the deceleration of the part of the vehicle body to which the seat is attached. As shown by the solid line, a deceleration level higher than the average deceleration is produced for a prescribed (short) time period in an initial phase (interval a in the drawing), and an opposite deceleration is produced for a short time period (interval b in the drawing) before the vehicle body starts decelerating at the average deceleration (interval c in the drawing). It has been confirmed by simulations conducted by the inventors that such a time history of the vehicle body deceleration is effective in reducing the overshoot of the vehicle occupant deceleration particularly owing to the reverse deceleration in interval b, and the vehicle occupant deceleration G1 can be significantly reduced as compared to the case of a constant deceleration (rectangular wave) for a given distance for deceleration (dynamic stroke).
For more details of vehicle body structures based on the foregoing concept, reference should be made to copending U.S patent applications Ser. Nos. 09/376,098 filed Aug. 17, 1999, 09/377,366 filed Aug. 18, 1999, 09/376,888 filed Aug. 18, 1999, 09/621,411 filed Jul. 21, 2000 (our ref: F684), 09/627,969 filed Jul. 28, 2000 (our ref: F685) 09/621,336 filed Jul. 21, 2000, 09/608,669 filed Jun. 30, 2000, 09/648,190 filed Aug. 23, 2000 (our ref: F688). The contents of these copending patent applications are hereby incorporated in the present application by reference.
The present invention is intended to improve previous proposals made in connection with the vehicle body structure based on the above described concept, and a primary object of the present invention is to provide a vehicle body structure which can favorably control the deceleration of the vehicle body supporting the vehicle seat at the time of a frontal vehicle crash so that the maximum deceleration of the vehicle occupant may be reduced.
A second object of the present invention is to provide a vehicle body structure based on the above described concept which is simple in structure, and requires minimum changes from the existing vehicle body design.
A third object of the present invention is to a vehicle body structure based on the above described concept which adds very little weight to the existing vehicle body design.
A fourth object of the present invention is to a vehicle body structure based on the above described concept which can produce a highly desirable deceleration time history for the vehicle seat at the time of a vehicle crash.
According to the present invention, such objects can be accomplished by providing an automotive vehicle body structure, comprising: a vehicle body main frame including a floor member defining a floor of a passenger compartment, a dashboard panel extending upright from a front end of the floor member, and a pair of front side beams extending between a front end of the vehicle body and the dashboard panel; a crash load transmitting member extending from a front end of the vehicle body to a part adjacent to the floor member; a vehicle seat connected to the crash load transmitting member; a guide member attached to the main frame for normally fixedly securing the crash load transmitting member but allowing the crash load transmitting member to move rearward of the vehicle body when the crash load transmitting member is subjected to a rearward force exceeding a prescribed threshold level; and a stopper which is fixedly attached to the main frame, and adapted to abut a part of the crash load transmitting member upon a rearward movement of the crash load transmitting member by a prescribed distance; the prescribed threshold level being smaller than a level that will cause a collapsing deformation of the crash load transmitting member.
Thus, the guide member normally retains the crash load transmitting member, which may comprise a sub frame for supporting an engine and/or a wheel suspension system, firmly to the vehicle body main frame as a part of the vehicle body, but allows the crash load transmitting member to move rearward, and hit the stopper so that the desired deceleration time history may be achieved in the crash load transmitting member which is integral with the seat so that the deceleration of the vehicle occupant may be favorably controlled.
Typically, the part of the vehicle body structure adjacent to the front dashboard panel is relatively rigid as compared to the rear end of the vehicle body so that an effective stopper can be formed in this part without requiring any special enforcement.
For even more efficient utilization of the material for the vehicle body, the guide member may be located adjacent to a lower end of the dashboard panel, and an enlarged part is provided in a part of the crash load transmitting member ahead of the guide member by the prescribed distance so that the guide member may serve as the stopper which abuts the enlarged part as the crash load transmitting member moves rearward by the prescribed distance. Thus, the weight increase that is required for improved crash safety can be minimized.
To achieve a highly favorable time history of the deceleration of the crash load transmitting member, particularly at the time the crash load transmitting member collides with the stopper, a cushioning member may be provided between the stopper or the guide member and the enlarged part of the crash load transmitting member. The cushioning member may consist of either a plastically collapsible extension of the enlarged part or a plastically collapsible extension of the guide member.
The retaining force of the guide member in retaining the crash load transmitting member can be easily attained by forming the guide member with a channel shaped bracket which surrounds a part of the crash load transmitting member so as to achieve a prescribed frictional retaining force. The frictional force can be suitably adjusted by using a suitable frictional lining or controlling the force used for fastening the guide member.
Alternatively, the guide member may comprise a rod which is passed through a longitudinal slot formed in one of the main frame and the crash load transmitting member and secured to the other of the main frame and the crash load transmitting member so as to achieve a prescribed frictional retaining force.
The guide may also comprise a rod which extends in the fore-and-aft direction from one of the main frame and the crash load transmitting member, and a hole formed in the other of the main frame and the crash load transmitting member to receive and retain the rod with a prescribed retaining force.